Nuclear shielding tensor, quantum-chemical

Solid-state high-resolution NMR spectroscopy, combined with quantum chemistry, is able to provide detailed information on the electronic and stereochemical structures of molecules[l]. Quantum-chemical calculations produce three principal values of the nuclear shielding tensor. These principal values have more detailed information about structure of molecules as compared with isotropic chemical shifts. Comparison of the observed chemical shift and chemical shift tensor with the calculated shieldings, produced by quantum-chemical calculations, permits deep insight into the structures of the molecules under investigation. 

For the quantum chemical calculation of NMR chemical shifts, it is essential to realize that the shielding tensor a in Eq. (6.3) appears in a term bilinear in the external magnetic field B and the nuclear magnetic moment nij of interest. This means that the shielding tensor is a second-order property... 

MD trajectory based on empirical polarizable force field and performed quantum chemical calculations of hyperfine couplings, g- and ZFS tensors and nuclear shielding terms at the snapshot configurations. Thus obtained fluctuations of the molecular properties were used to estimate the Curie-type paramagnetic relaxation contribution (which is a paramagnetic analogue of the CSA relaxation in the diamagnetic systems) to the NMR relaxation of aqueous protons. 

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